1. Field of the Invention
The present invention relates in general to an air conditioner and more particularly to an apparatus for controlling the air conditioner in response to a variance of an electric voltage supplied to the air conditioner from a power source.
2. Prior Art of the Invention
An air conditioner of the type which is called as a separation-type air conditioner is constructed primarily of an outdoor unit and a room unit and these two units are composed of devices and appliances which constitute a refrigeration cycle, as compressors, and are connected with each other by refrigerant pipes and demand signal wires.
The room unit has a room side heat exchanger, a fan motor, a room fan which is driven by the fan motor and circulates the air heated/cooled by the room side heat exchanger, a port for connection of refrigerant pipes, a room side controller, etc.
The outdoor unit has an outdoor heat exchanger, an outdoor fan which is composed of a motor and propeller fan, for facilitating the heat exchange between the outdoor air and the outdoor side heat exchanger, a compressor, a motor for driving the compressor, four-way valves for switching the circulating direction of the refrigerant, a check valve (non-return valve) for limiting the circulation direction of the refrigerant, an electromagnetic valve for controlling a flow rate of the refrigerant which is supplied to the room unit, a capillary tube (an expansion device), a strainer, a port for connection of refrigerant pipes, an accumulator, a muffler, and an outdoor side controlling device (outdoor unit control board), and the devices described above are connected with each other directly or indirectly so that a predetermined refrigeration cycle is formed.
A detailed description of the refrigeration cycle will be omitted for simplification only because a generally known refrigeration cycle can be used in the air conditioner of present invention.
In a cooling operation, the refrigerant discharged out of the compressor is condensed by the outdoor heat exchanger and expanded by the capillary tube and then evaporated by the room side heat exchanger, so that a cooling operation is achieved in the room to be air conditioned.
In a heating operation, the refrigerant discharged from the compressor is condensed by the room side heat exchanger and expanded by the capillary tube and then evaporated by the outdoor side heat exchanger. A heating operation for a room to be air-conditioned is accomplished by utilizing the heat of condensation at the time of condensation of the refrigerant by the room side heat exchanger.
In order to proceed cooling, heating or drying operations (wherein the drying operation is conducted by using the same refrigerant flow as the cooling operation and automatically controlling a blowing rate of the room fan) in a separate type air conditioner having a room unit and outdoor unit as described above, a controlling signal is transmitted from the room unit to the outdoor unit through a communication line. A general electric circuit of the air conditioner to which the present invention relates will be described with reference to FIG. 1.
In FIG. 1, a signal from the room unit 2 is supplied to a terminal 3 of a terminal plate A (connector 6) through a signal line and then transmitted to a serial communication circuit of a control portion (outdoor unit control substrate 3) of the outdoor unit 1. Besides, an electric power which is controlled by the room unit 2 is supplied to a terminal 1 and a terminal 2 of the terminal plate B through terminals 1 and 2 of the terminal plate A (connector 6) and is supplied through a noise filter to a rectifying circuit 8 and an inverter circuit 9 for driving the compressor 5.
When a power source of 200 V of a single phase is connected to the terminal plate B, the rectifying circuit 8 is switched to comply with the 200 V of a single phase and the connection between the terminal plate A and the terminal plate B is cut off.
The controlling portion (outdoor unit control substrate) 3 of the outdoor unit 1 which receives an operation demand is controlled with respect to a rotational speed of the outdoor fan motor 7, an opening degree of the refrigerant controlling electromagnetic valve 4 which controls a flow rate or an expansion amount of these refrigerant, and an operational capacity (rotational speed) of the compressor, so that a room temperature is shifted to a set temperature which is predetermined in the room unit 2.
In FIG. 2 showing a principal portion of an electric circuit of the control portion which is mounted on the room unit 2, a microcomputer 21 is provided with a switch device for setting a basic mode of the air conditioner, an operational display and an electric circuit which receives a signal from a remote controller (not shown).
The microcomputer 21 serves to control the operation of the air conditioner in accordance with the signal transmitted from the remote controller. Based upon the setting of operations of cooling/heating/blowing, a flowing direction of the refrigerant is changed, by way of the terminal 3 of the connector 6A in case of a heating operation, and a signal for switching ON the four-way valve is transmitted to the control portion of the outdoor unit 1 so that a cooling operation and a heating operation are switched by the four-way valve.
A stepping motor 23 serves to change an angle of the flap to change vertically and transversally the discharge direction of the conditioned air which is discharged from the room unit 2. A motor 22 drives a cross flow fan for a blowing operation and its rotational speed is automatically or otherwise optionally controlled. A driving circuit for this motor 22 is controlled by the microcomputor 21. In the figure of the drawing, reference characters TH1 and TH2 are temperature sensors which detect a room temperature and a temperature of the refrigerant heat exchanger, respectively.
In FIG. 3 which shows an electric circuit of a principal portion of the controlling portion of the outdoor unit 1, a connector 6B is connected with the connector 6A of the connecting portion of the room unit 2 shown in FIG. 2 such that the terminals of the same terminal number in connectors 6A and 6B are connected with each other. Here, the terminal plate 6B is shown as being a combined structure between the terminal plates A and B in FIG. 1.
The serial circuits are provided for the purpose of communication between a microcomputer 21 of the room unit 2 and a microcomputer 31 of the outdoor unit 1, and the room unit 2 is provided with a serial circuit 20 and the outdoor unit 1 is provided with a serial circuit 30.
The microcomputer 31 of the outdoor unit 1 serves that its operation demand is transmitted from the room unit through the serial circuit 30 to control the compressor motor 5, four-way valve switching solenoid RV, and the fan motor 7.
The compressor motor 5 uses an AC motor, and DC power which is voltage doubler rectified by a rectifier circuit 8 is converted to an AC power of pseudo-sine wave based upon the PWM theory by an inverter circuit 9 and then supplied. The fan motor 7 is a brushless DC motor and its rotational speed is controlled in accordance with signals from the microcomputer.
The four-way valve switching solenoid RV serves to switch the state of the four-way valve in accordance with the transmission direction of an electric power. Accordingly, switching of the transmission direction of the electric power of the solenoid RV permits the refrigeration cycle to be changed to heating/cooling operation. Reference characters TH3, TH4 and TH5 are temperature switches each of which serves to detect the temperature of its predetermined portions and transmit the detected data to the microcomputer 31.
In the air conditioner constructed as described above, when the power source voltage supplied to the driving source such as the compressor motor and so forth is varied extensively to a protection range beyond a normal operation region, in other words, if the voltage is raised more than the predetermined value relative to a reference voltage, an over-voltage is added to windings of the motor with a result of possible burning of the motor, and if the voltage drops below the predetermined value relative to a reference voltage, it results in lacking of motor torque and stalling torque (locking) for the motor.